In the construction industry, shoring is widely used to support forms for concrete construction of buildings, bridges and other structures. Flying forms such as those described in a copending U.S. application Ser. No. 07/653,549, filed Feb. 11, 1991, can be used to construct buildings using a flying form method. Other types of support structures are described in an earlier U.S. Pat. No. 4,470,574. Once the concrete has initially cured, the support structure is removed and advanced to other locations. However, the concrete has not yet fully cured and able to support its own weight load and the additional loads of additional shoring and other equipment and the new concrete being poured as upper floors. Accordingly shoring posts are used to support the curing concrete structure until it has sufficiently cured.
Shoring posts are well known in the art. Shoring posts of the prior art include U.S. Pat. Nos. 3,870,268 and 3,847,340. Generally shoring posts comprise a telescoping sleeve slidably mounted in a support post. The sleeve has a plurality of aligned diametrically extending holes through which a pin can be inserted. The length of the shoring post can be roughly fixed by inserting the pin through the hole nearest the desired height. A screw thread is mounted on the post or machined into the outer surface of the post and a threaded nut or handle is advanced to extend the post until it fully supports the load.
Shoring posts of the prior art perform reasonably adequately. However at times, unloading the shoring posts can be difficult. Since the shoring post is under a compressive load, especially if the shoring post is used to support forms in which concrete is poured, the adjusting nuts on the shoring post are often difficult to unscrew. Hammers are often used to unscrew the nut of the screw jack. Since the screw thread is normally adapted for incremental extensions of the shoring post between adjusting holes, unscrewing the post nut in this manner is time consuming.
In U.S. Pat. No. 3,870,268, a release slide is described. The release slide has a thicker portion and a thinner portion which extends diametrically through holes between the lower tube and the telescoping tube. The slide is urged across from the thicker portion to the thinner portion reducing the length of the shoring post releasing the pressure acting thereon. The holes through which the release slide acts is often damaged during normal usage. The release slide normally has a circular cross-section. This geometry results in the pressure loads to be transmitted from the telescoping tube to the outside lower tube through two diametrically opposed points. The holes in the telescoping tube and the lower tube often become deformed out of shape dramatically reducing the life of the shoring post.